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Re: [PATCH v2 2/6] mac80211: Support getting sta_info stats via ethtool.

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On 04/17/2012 09:00 PM, Johannes Berg wrote:
On Tue, 2012-04-17 at 20:46 -0700, Ben Greear wrote:

+	rcu_read_lock();
+	list_for_each_entry_rcu(sta,&local->sta_list, list) {

This doesn't seem right -- shouldn't it look up the BSSID or something
and only work on managed interfaces? What if there really are two
stations on this interface -- then it'll just overwrite it and return a
random station's data? That's useless.

Well, its weird at least.

But, if there are multiple stations, like for APs??, then it will
add the station's stats together.  Perhaps not horribly useful, but better
than nothing.

Oh, right, it's adding, I missed that. But is that really useful?

It provides a summary for AP, and precise stats for managed station
mode (excepting TDLS where it may return sums, it seems).

I could just return all zeros for non managed
station interfaces, but I *have* to return some value, so it seems
little loss to just add the station stats together.

For managed interface, I *think* they don't have more than one station, right?

You can't rely on it. Typically they will, but with TDLS there might be
multiple.

And, as for the underlying driver stats and survey stats (in later patches),
that is only probed once.  I guess if you somehow had two
stations on different channels on the same network device,
the survey stats would be a bit dodgy, but it does return
the freq for the stats in question, so at least you know
what you are getting.

A single netdev is always going to be on a single channel. Actually, I
take that back, I think TDLS can work out of channel too, but we don't
support that right now.

So, based on your response, a sum still seems most useful to me.  The ethtool
API gives no way to request any subset of stats, so all I can key off of
is the netdev.

I have some plans percolating to add some new ethtool API to get subsets
of stats, but that is likely a ways off, and of course it may not be
accepted regardless.

Thanks,
Ben


--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc  http://www.candelatech.com

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